Spacecraft, satellites or the like may include a space platform mounted thermal or solar energy system. Solar energy receivers of various sorts are employed to power on-board systems while in orbit, for instance. Since, in many instances, the orbit of the spacecraft or satellite follows a path that is in the interposition of the earth between the sun, thereby blocking the solar energy receiver from the source of solar energy, some sort of energy storage device is required. In other words, solar energy receivers normally are designed to receive sufficient energy to power on-board systems while illuminated by the sun as well as to provide sufficient energy to an energy storage device as to operate the systems when the receiver is not so illuminated.
Other considerations include the concern of reliability of the system. A breakdown in a system in a spacecraft may endanger the mission of the spacecraft and, because satellites are not easily retrieved, it is necessary that the systems be highly reliable and not subject to failure in hostile environments of space.
For instance, one of the areas of most concern and unreliability is the apertured radiation shield constructed about the solar energy receiver. Shields may be completely fabricated of rigid and/or structural components, and coated with a rigid or brittle ceramic material on a substrate structure. Such constructions may experience cracking problems during launch and subsequent orbital thermal cycling.
The complex needs served by the radiation shields often are compromised to accomplish other functions. Such shields must have high infra-red emittance and low solar absorption to minimize temperature excursions due to impingement of solar radiation. The shields must have high temperature capability to survive during "off-pointing" conditions when concentrated solar energy is incident upon the radiation shield. The shield also must have good infrared radiation insulation properties to reduce radiation losses from the solar energy receiver through the shield.
This invention is directed to solving the above problems while still satisfying the complex needs required of an apertured radiation shield.